Process of making a battery plate grid

ABSTRACT

A process for making a battery plate grid, the grid being formed from a fan-like conductor and a grate-like nonconductor bonded one to the other by a plurality of fusion-interlocked joints.

United States Patent Wheadon et a].

[ 51 July 25,1972

PROCESS OF MAKING A BATTERY PLATE GRID [72] Inventors: Ellis G. Wheadon,Yorktown; Norman L.

Willmann, Anderson, both of lnd.

General Motors Corporation, Detroit, Mich.

[22] Filed: May 18, 1970 [21] Appl.No.: 38,441

[73] Assignee:

Related U.S. Application Data [62] Division of Ser. No. 780,068, Nov.29, 1968, Pat. No.

[52] U.S. Cl ..264/249 [51] ..H01j 35/04, HOlm 35/00 [58] Field ofSearch ..264/249, 248-252, 264/271-274, 294, 331; 136/54, 55, 58, 63, 59,

[56] References Cited UNITED STATES PATENTS 1,008,029 1 1/191 1 Gorman..264/249 X 3,491,183 l/1970 Brow ..264/249 3,595,700 7/1971 Rosansky..264/249 FOREIGN PATENTS 0R APPLICATIONS 691,712 5/1953 Great Britain..136/58 1,935,803 3/1970 Germany ..136/36 Primary Examiner-Robert F.White Assistant Examiner-Willard E. Hoag AtlorneyWilliam S. Pettigrew,R. .1. Wallace and Lawrence B. Plant [57] ABSTRACT A process for makinga battery plate grid, the grid being formed from a fan-like conductorand a grate-like nonconductor bonded one to the other by a plurality offusion-interlocked joints.

2 Claims, 7 Drawing Figures PROCESS OF MAKING A BATTERY PLATE GRID Thisapplication is a division of application Ser. No. 780,068 entitledBATTERY PLATE GRID", filed Nov. 29, 1968 in the names of Ellis G.Wheadon and Norman L. Willmann, and assigned to the assignee of thisapplication.

Application Ser. No. 780,068 is now US. Pat. No. 3,556,854, issuedJan.I9, 197].

In recent years, there has been a trend toward producing lighterbatteries. A convenient way to do this is by reducing the weight of suchelements as the case, top, grids, connectors, etc. Lightweight grids ofplastic or the like are therefore becoming more commercially important.With the advent of plastic grids has come the requirement for developingtechniques for attaching conductive elements to the comparativelyfragile plastic supports in a manner such that they will not come looseduring subsequent handling and service. This invention relates to animproved lightweight composite battery plate grid and a technique forforming same.

It is an object of this invention to provide a light-weight,lead-conserving battery plate grid which is a composite of amulti-fingered conductor and a finger-spacing, nonconductive, fusiblecarrier joined at a plurality of fusion-interlocked joints.

This invention comprehends battery plate grids which are composites ofmultifingered, fanned-out conductors and carriers therefor which arejoined together at a plurality of fusion interlocked joints. Thecarriers may comprise simply a series of parallel strips which intersectand space the fingers one from the other. In a preferred form,fusion-interlocking is accomplished by superposing a fanned conductoratop a fusible, plastic nonconductor (e.g., a perforated sheet). Theconduc tor has a plurality of electrically conductive fingers divergingfrom a common juncture. A heated plate is caused to rest upon theconductor. When the conductor gets hot enough, the plastic in contactwith the conductor fuses (softens) and at the same time pressure isapplied by the plate to press the conduc' tor into the nonconductor. Inits most preferred form, the nonconductor is a grate-like sheet having aborder and a plurality of oblong shaped grid wires intersecting theborder and the conducting fingers have locking grooves therein intowhich the fused nonconductor flows and hardens to form an introfused,interlocked joint. The fusible nonconductor also flows around thefingers and upon hardening forms a circumfused, interlocked joint.

FIG. I is an elevational view of a composite battery grid in accordancewith this invention.

FIG. 2 is a partially sectioned view taken along the lines 2 2 of thegrid shown in FIG. 1.

FIG. 3 is a partially sectioned perspective view taken along the line 33ofthe battery grid shown in FIG. I.

FIG. 4 is an elevational view of another grid formed in accordance withthis invention.

FIG. Sis a partially sectioned perspective view ofa grid wire takenalong the lines 5-5 of FIG. 4.

FIGS. 6 and 7 depict other embodiments of applicant's invention.

FIG. I shows a composite battery plate grid which is comprisedprincipally of a perforated plate 2 and a fanned-out conductor 4. In itspreferred form the nonconductive perforated plate 2 comprises a border 6and a number of grid wires 8. The grid wires 8 extend across the face ofthe plate 2 and intersect the borders 6 so as to form a generallygrate-like structure. For purposes of this invention, it is preferredthat a major portion of the grid wires 8 extend diagonally across theperforated plate 2 rather than parallel to the borders. The conductor 4comprises a juncture I0 and a plurality of fingers 14 which diverge fromthe juncture 10 in a fan-like manner so as to extend across the face ofthe perforated plate 2. In its most convenient form, the conductor 4initially comprises a ribbon of metal (i.e., lead) which has been slit anumber of times to provide the fingers 14. Prior to joining theconductor with the nonconductor, the fingers 14 are flared outwardlyfrom the juncture 10. The use of the word juncture herein is merelyintended to refer to that portion of the conductor where the severalfingers meet to form a single conductor, i.e., an electrical confluence.It is not intended that the word juncture be limited to a one-piececonductor but may, of course. include a braided or equivalent conductorformed by the several fingers 14. A plate lug 12 is provided as a meansfor withdrawing the current from the plate and is most conveniently acontinuation of the conductor, e.g., extended juncture. Locking grooves16 are provided in the fingers l4 and preferably the juncture 10. Thelocking grooves 16 are undercut, e.g. as dovetails or the like, as bestshown in FIGS. 2, 3 and 6 The perforated plate 2 is comprised of amaterial which is fusible at a temperature below that of the conductive.It is herein intended that the word fusible" be used in the more generalsense of being susceptible to reduction to at least the plastic state byheat. The nonconductor is preferably polypropylene but other polymerplastics may also conveniently be used. As will be discussed in moredetail hereinafter in connection with the process for fabricating thecomposite grid, a plurality of fusion interlocked joints 18 are formed.In FIGS. 1, 2 and 3 the fusion interlocked joints l8 depicted are of theintrofused type wherein the fusible nonconductor flows into a cavity orlocking groove in the conductor 4. In FIGS. 6 and 7, the fusioninterlocked joint depicted is of the circumfused type wherein thefusible nonconductor flows around the conductor to form the joint.

FIG. 2 is an exploded view of the nature of the fusion-interlocked jointprovided at the locus of intersection of the juncture l0 and the border6. A number oflocking grooves 16 are provided in thejuncture 10 as wereprovided in the several fingers 14. As a result, at the time of bondinga plurality of fusion-interlocked joints are provided between thejuncture and the border. These joints 18 are of the introfused type.

FIG. 3 depicts a partially sectioned exploded perspective view of aportion of the grid shown in FIG. 1 and more clearly depicts the natureof the several fusion-interlocked joints 18 formed between the severalgrid wires 8 and fingers 14. In this embodiment the locking grooves 16are of the dovetail type.

FIG. 4 depicts another embodiment of the invention but differs from thatdisclosed in FIG. I, primarily with respect to the number andarrangement of the grid wires 8. In the FIG. 4 embodiment considerablymore grid wires are provided in the one direction and a number ofadditional grid wires are provided in another direction normal to thedirection of the first grid wires. This arrangement generally providesfor a somewhat stronger grid. It is also noted that the border 6 has,for the must part, a smaller dimension than that shown in FIG. I and asa result the need for the additional grid wires 8 becomes more apparent.A widened portion 20 of the border 6 may be provided to insure a goodfusion-interlock between the juncture 4 and the border 6. Anotherdistinction between the embodiments shown in FIGS. 1 and 4 is that thelocking grooves 16 formed in the conductor 4 have been formed diagonallyinto a much larger lead ribbon and a conductor having an appropriatelyshaped juncture and lug l2 stamped therefrom prior to the flaring andsetting of the fingers 8.

FIG. 5 depicts another aspect of this invention and shows in exploded,sectioned, perspective view a grid wire 8. In section the grid wire 8 isoblong having a major axis a-a and a minor axis bb. In this particularembodiment the grid wire 8 is generally rectangular in shape. Otheroblong shaped grid wires, such as ellipses or the like, may convenientlybe used as shown in FIGS. 6 and 7. ln forming the composite grids ofthis invention, it is preferred that the grid wires 8 be oriented suchthat the major axis a-a is normal to the fingers 14 (See FIG. 6). Theadvantages of this arrangement will be more clearly discussedhereinafter.

FIGS. 6 and 7 depict other embodiments of applicantss invention. FIG. 6discloses the use of a grid wire 8 having generally an elliptical crosssection and in which two fusion interlocks are formed simultaneously,the first being of the circumfusion type 18a and the second being of theintrofusion type 18b. FIG. 7 shows an elliptically shaped grid wire 8 incircumfused relation to a rounded conductive finger 14.

Although not shown on the drawings, it is most convenient to also formfusion-interlocked joints between the ends of the several fingers 14 andthe grid border 6.

ln preparing the composite grid, the nonconductive perforated plate isformed to the desired configuration. It may be molded or punched. Theperforated sheet may be comprised simply of a sheet of plastic having aplurality of holes punched therein or as in the preferred form, it iscomprised of a border and a plurality of 1 grid wires intersecting oneanother and the grid border to form a grate-like structure. By the wordgratelike" I intend to include structures which are similar to gratesand comprise a frame of parallel bars or a lattice of crossbars.

It is preferable that the bars, which are herein referred to as the gridwires, be oblong such that they have both a major and minor axis withthe minor axis being substantially parallel to the principal plane ofthe grid and the major axis being substantially normal to the principalplane of the grid. By having the major axis substantially normal to theprincipal plane of the grid and therefore substantially normal to theconductor, distinct benefits are obtainable. During thefusion-interlocking step, which will be described hereafter, theconductive fingers sink deeply into the grid wires in the direction ofthe major axis with less chance of melting completely through the wires.

ln' the process for making the composite grid, the conductor 4 is formedfrom a strip of lead which has a number of locking grooves formed in onesurface thereof. The strip is cut between the grooves to form theplurality of fingers. An end portion of the strip is left unslit andforms the juncture of the many fingers, as well as the lug for theplate. The fingers are fanned out from the juncture and diverge in asmany directions as is necessary to adequately provide good electricalconductivity through the plate. The thus fanned conductor is placed atopthe nonconductive, grate-like fusible support with the grooved sidecontacting the plastic. A heated plate is placed on the conductor andtransfers its heat to the conductor. After the conductor is thuslyheated, pressure is applied to the plate which causes the heated wiresto sink into the fusible nonconductor. The nonconductor fuses only atthe points of intersection of the heated conductor and the nonconductor.The fused portions of the nonconductor flow into the locking grooves andaround the wires. Upon cooling, a tight, fusion-interlocked weld orwelds result at each of the fusion points. By fusion-interlock betweentwo members, as used herein, is meant merely an interlocking jointresulting from the fusion and flow of one of the members into or aboutthe other member such that a mechanical bond between the two is formedwhether it be of a circumfused or introfused type or both. By anintrofused joint is meant one which has been formed by the flow of thefused material into an anchoring cavity or the like in the other member.By a circumfused joint is meant one which is formed by the flow of thefusible material around the other member.

In one specific example of the invention, a nonconductive grate-likesupport, such as shown in FIG, 1, is comprised of I talc-filledpolypropylene wherein the talc may vary from about 20 percent to about40 percent. The 20 percent talcfilled polypropylene has a softeningpoint of about 240 F., whereas the 40 percent talc-filled polypropylenehas a softening point of about 270 F. The conductor comprises a leadalloy containing a small proportion of calcium. The grate-likenonconductor is about 0.060 inch thick along the major axis of the gridwire. The conductor is about 0.040 inch thick. The conductor is laidatop the plastic and preheated with a metal platewhich is at atemperature of about 450 F. This preheating lasts about Vz second.Subsequently about 200 lbs/inch of pressure is applied to the plate topress the conductor intothe plastic. Mechanical stops are provided toinsure that the conductor does not cut through the grid wire.

While the invention has been disclosed solely in terms of certainspecific embodiments thereof, its scope is only limited to the extenthereinafter defined.

We claim:

1. A process for manufacturing thin, light-weight, lead-acid storagebattery grids comprising the steps of:

forming, in a first plane, fan-llke array of lead-rich electricallyconducting fingers diverging from a common junction each of said fingershaving anchoring cavities therein;

forming, in a second plane, finger-spacing carrier me for said array,said means comprising a light-weight, substantially nonconducting,fusible material having a softening point lower than said fingers;

juxtaposing said array and said carrier means such that said planessubstantially parallel each other; heating said array sufficiently tocause softening of said fusible carrier at the loci of intersection ofsaid array and said carrier;

pressing said array and said carrier together to imbed said array insaid carrier at said loci and thereby merge them into an approximatelycoplanar composite grid and to cause said fusible material to flow intosaid anchoring cavities and at least partially around said fingers; and

cooling said composite to affix said array to said carrier by aplurality of fusion-interlock joints extending throughout the principalplane of said grid.

2. The process of claim I wherein said anchoring cavities are lockinggrooves extending longitudinally along said fingers.

1. A process for manufacturing thin, light-weight, lead-acid storagebattery grids comprising the steps of: forming, in a first plane,fan-like array of lead-rich electrically conducting fingers divergingfrom a common junction each of said fingers having anchoring cavitiestherein; forming, in a second plane, finger-spacing carrier me for saidarray, said means comprising a light-weight, substantiallynonconducting, fusible material having a softening point lower than saidfingers; juxtaposing said array and said carrier means such that saidplanes substantially parallel each other; heating said arraysufficiently to cause softening of said fusible carrier at the loci ofintersection of said array and said carrier; pressing said array andsaid carrier together to imbed said array in said carrier at said lociand thereby merge them into an approximately coplanar composite grid andto cause said fusible material to flow into said anchoring cavities andat least partially around said fingers; and cooling said composite toaffix said array to said carrier by a plurality of fusion-interlockjoints extending throughout the principal plane of said grid.
 2. Theprocess of claim 1 wherein said anchoring cavities are locking groovesextending longitudinally along said fingers.